Brothers Jimmy O'Farrell (a police officer) and John O'Farrell (a police surgeon) begin to suspect their brother Dennis is a racketeer after a shooting occurs in front of their parent's brownstone and John treats a beating victim in Dennis' apartment. Dennis' family believe that he is a successful businessman, when in fact, he is the leader of the infamous Muller gang. Dennis is using the name Barney Muller. Jimmy promotes to detective and proposes to his girlfriend, Kathleen. Shortly thereafter, Kathleen attends a party given by "Muller" She learns that Muller's henchman "Silk" is the gunman involved in the murder in front of the O'Farrell apartment. Kathleen tells Jimmy, but she is overheard by one of Muller's men, and plans are made to dispose of Kathleen and Jimmy. Dennis realizes his cover has been blown and he learns of the plot against Jimmy. Dennis and John rush to warn Jimmy but they arrive just as Jimmy is being ambushed. Dennis saves Jimmy, but is shot by his own gang. Dennis dies in the arms of Jimmy and John, who tell their parent that Dennis has gone on another mysterious trip, perhaps this time, for good.